Professor Andy MacMillan, the Scottish architect, who has died aged 85, was, with Isi Metzstein, a member of one of the most influential architectural partnerships in Britain, working in the style of Le Corbusier and Frank Lloyd Wright; however, their most famous work, St Peter’s Seminary at Cardross, Dunbartonshire, was once described as the place “where Modernism crawled up a hill to die”.

MacMillan and Metzstein worked together at the Glasgow firm of Gillespie, Kidd & Coia, and later taught at the Mackintosh School of Architecture. In the 1950s they collaborated on the St Paul’s project at Glenrothes, Scotland’s second post-war New Town. Later they designed the library at Wadham College, Oxford; the halls of residence at the University of Hull; and the red-brick Robinson College at Cambridge, which in 1983 received an award for architectural excellence from the Royal Institute of British Architecture and in 2008 appeared in The Daily Telegraph’s top five “Most Inspiring Buildings in Britain”.

Andy MacMillan (KIERAN DODDS)

But St Peter’s Seminary, a three-storey concrete ziggurat on the banks of the Clyde, inspired by Corbusier’s chapel at Ronchamp and his monastery at La Tourette, was considered their masterpiece. Completed in 1966, it was designed with a sympathetic understanding of the ritualised nature of seminary life that was perhaps surprising in a lapsed Protestant (MacMillan) and a Jewish atheist (Metzstein).

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Each of the activities that made up the trainee priest’s day was given its own setting — from a glass-sided refectory to an airy sky-lit chapel with a vast granite altar — providing an environment in which the choreography of Roman Catholic ritual could be performed in spiritually uplifting space and light.

The seminary won acclaim even from such traditionalist journals as Country Life for its design and fine workmanship (the interiors were panelled in solid wood, echoing the style of Charles Rennie Macintosh). It was voted Scotland’s best modern building by the architecture magazine Prospect, and in 1967 it won Gillespie, Kidd & Coia an award from RIBA. It was also one of only 42 post-war buildings in Scotland to be Grade A listed.

The outside of St Peter's Seminary when it was first built

It also, however, attracted fierce criticism, which grew in volume as reports appeared of ill-fitting windows, door handles falling off, the chapel flooding and ominous creaks emanating from the beams that soared above the sanctuary.

Ultimately, though, it was the Second Vatican Council’s decision to train priests in local communities rather than at seminaries that proved its undoing. After just 14 years the seminary shut down, in 1980, and the building was subsequently abandoned to the elements and the vandals. Within a few years it was reduced to a graffiti-covered skeleton, named as one of the world’s most endangered sites by the World Monument Fund.

As Frank Arneil Walker put it in The Buildings of Scotland, “in little more than a generation, God, Le Corbusier and Scottish architecture have all been mocked”. MacMillan’s verdict was: “It’s terrible to live in a culture that can allow a building like that to be treated that way.”

Despite a number of proposals for reuse or renovation of the building, its future remains in doubt.

The interior of the abandoned St Peter's Seminary in Cadross (ALAMY)

Andrew MacMillan was born prematurely on December 11 1928 in a tenement in the Maryhill district of Glasgow. His father, an unemployed railway clerk, improvised an incubator for his son, without which he probably would not have survived infancy.

At North Kelvinside Secondary School, MacMillan proved an able all-rounder and was entered for the “corporation exam” for an apprenticeship with Glasgow Corporation (now Glasgow City Council). He passed, and was interviewed by the chief architect and the chief surveyor. “The surveyor told me what a terrible job surveying is, so I chose architecture,” he recalled.

During his apprenticeship he took evening classes at Glasgow School of Art, where he met Isi Metzstein, then working as an apprentice at Gillespie, Kidd and Coia, one of Britain’s most respected architectural practices.

MacMillan worked for the corporation for seven years, and by the age of 20 was running his own projects: “I had five buildings for the corporation and 15 shopping centres. I worked on housing that varied from a prefabricated stone house to bog-standard tenements.”

He then spent two years with East Kilbride new town, but became increasingly frustrated by local government bureaucracy. In 1954, when Metzstein mentioned that there was a vacancy at Gillespie, Kidd and Coia, MacMillan jumped at the chance.

The practice had been founded in the 19th century, but from the 1930s its principal client had been the local Roman Catholic archdiocese. It had been built up by the firm’s partner Jack Coia, a devout Catholic who, before the arrival of his young protégés, designed decent but unadventurous churches along traditional lines.

Like many young architects of their generation, MacMillan and Metzstein were passionate converts to Modernism; and from 1957, when they effectively assumed creative control of the practice’s output, they began to produce an extraordinary string of Modernist buildings

Their first project, St Paul’s, Glenrothes, completed in 1957, was described as “the first modern church in Britain”. They went on to build 17 churches and chapels throughout central Scotland, following in the wake of new town development and urban housing schemes, culminating with the completion of the church of St Columba in East Kilbride in 1979. There were also the college buildings in Oxford and Cambridge, schools in Glasgow and Cumbernauld, and a maternity hospital in Bellshill.

But the churches were what they were known for. As Metzstein once explained, their aim was to “strip out the rubbish”, doing away with aisles, naves, columns and other gothic paraphernalia. Luckily the Church, itself undergoing a period of modernisation, seemed to like what they came up with.

MacMillan became a partner of the firm in 1966 and served as Professor of Architecture at Glasgow University and head of the Mackintosh School of Architecture from 1973 to 1994. His teaching at the school with Metzstein, who died in 2012, was credited with making it one of the best architectural training establishments in the world.

In his later years MacMillan served on architectural judging panels and as a government adviser. He was a member of the Scottish Arts Council from 1978 to 1982, and a member of the panel that chose Enric Miralles’s design for the Scottish Parliament in Edinburgh — a project that brought criticism from locals not only for its appearance (like “upturned boats”) but also for its spiralling cost.

In 2001 MacMillan caused a furore when he lashed out at those citizens of Edinburgh who did not appreciate the finer points of the building, declaring them introspective, ignorant, and “not cultured the way that Glasgow hooligans are cultured”.

“What’s the highlight of an Edinburgh businessman’s life?” he inquired sarcastically. “He gets to be made a member of the Royal Company of Archers. He gets to wear a funny hat and walk about with a bow and arrow — a businessman in the 21st century!”

Among many awards, MacMillan won the RIBA Award for Architecture on four occasions and the Royal Scottish Academy Gold Medal in 1975. He was appointed OBE in 1992.

At the time of his death he was vice-president of the Glasgow School of Art.

He is survived by his wife, Angela, and by their son and three daughters.